| 翻訳と辞書 |
| Oxygenated treatment ： ウィキペディア英語版 |
Oxygenated treatment
Oxygenated treatment (OT) is a technique used to reduce corrosion in a boiler and its associated feedwater system in flow-through boilers.
Traditionally, corrosion was prevented by keeping the oxygen in the system below 10 ppb by using a deaerator and injecting an oxygen scavenger. This process is called All-volatile treatment (AVT) in reference to the volatile alkalizing agents added to the feedwater. Ammonia (NH3) is added to keep the feedwater pH high, thus reducing the risk of FAC. In AVT(R), a reducing agent is added. AVT(R) causes the formation of a protective layer of magnetite (Fe3O4), which is a combination of FeO and Fe2O3. In AVT(O), no reducing agent is added and residual oxygen is present. AVT(O) allows a layer of hematite to form on top of the magnetite, similar to oxygenated treatment.
With oxygenated treatment, oxygen is injected into the feedwater to keep the oxygen level between 30-50 ppb. "Common injection points are just after the condensate polisher and again at the deaerator outlet." 〔Brad Buecker, "Flow-Accelerated Corrosion: A Critical Issue Revisited", 2007, Power Engineering, http://www.power-eng.com/articles/print/volume-111/issue-7/features/flow-accelerated-corrosion-a-critical-issue-revisited.html〕 This forms a thicker protective layer of hematite (Fe2O3) on top of the magnetite. This is a denser, flatter film (vs. the undulation scale with OT) so that there is less resistance to water flow compared to AVT.〔Mitsuhiro Yamagishi, Masamichi Miyajima, "Evaluation of Oxygenated Water Treatment" 14th International Conference on the Properties of Water and Steam in Kyoto, August 29-September 3, 2004〕 Also, OT reduces the risk of flow-accelerated corrosion.〔Daniels, D., "HRSG Failure Mechanisms - Waterside," Proceedings of the 22nd Annual Electric Utility Chemistry Workshop, Champaign, Illinois, May 7–9, 2002.〕
When OT is used, conductivity after cation exchange (CACE) at the economiser inlet must be maintained below 0.15μS/cm 〔IAPWS Technical Guidance Document: "Volatile treatments for the steam-water circuits of fossil and combined cycle/HRSG power plants (July 2010) http://www.iapws.org/techguide/Volatile.html"〕 this can be achieved by the use of a condensate polisher.〔Frank Gabrielli and Horst Schwevers, "Design Factors and Water Chemistry Practices - Supercritical Power Cycles" PREPRINT-ICPWS XV Berlin, September 8–11, 2008〕
== Comparison of AVT to OT ==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Oxygenated treatment」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|